Cathode for electrical discharge devices



Oct. 1, 1957 H. KATz 2,808,530

CATHODE FOR ELECTRICAL DISCHARCE DEVICES Filed March 19, 1952 llllill/llllllIlIIIlllllllIII/IQ Unite States CATHODE FOR ELECTRICAL DISCHARGE DEVCES Helmut Katz, Erlangen, Germany, assgnor to Siemens & Halske Aktiengesellschaft, Berlin, Germany, a corporation of Germany This invention is concerned with a dispenser type cathode for electrical discharge devices comprising an emitter body and having a supply of an emission substance which migrates in operation through said body to the emission surface formed thereby.

One object of the invention is to improve the operation of a cathode of this type by making the emitter body partly or wholly of carbonaceous material, or by providing a layer of carbonaceous material thereon.

Pertinent antecedents are briey reviewed below so as to aid in the understanding of the invention.

The migration of the emission substance to the surface of the emitter body may be obtained by winding wires, strips or the like about such body so as to form tine passages through which the emission material can migrate or by making the body of sintered porous material containing such passages. The emitter body may be made of tungsten or molybdenum which are particularly favorable when using thorium or barium compositions as emission substance.

It has now been discovered that the migration and emission elect may be improved in such cathodes by the use of carbonaceous substances. Based on the recognition of this fact, the invention proposes to provide on the emitter body a carbonaceous layer, or to make it partly or Wholly of a carbonaceous material.

It has also been discovered that the emission may be improved by the use of admixtures of various materials. The invention therefore proposes, in accordance with another object, to provide within or on the emitter body admixtures or coatings containing individually or in combination the metals silicon, titanium, aluminum, iron, magnesium and calcium. These metals, individually or in combination, may be provided on the emitter body in the form of a thin coating.

The emitter body, in addition, may be provided with the previously mentioned carbonaceous layer or may be made partly or wholly of carbonaceous material, either of which may be porous.

It is further possible to make the emitter body of a sintered high melting metal forming line capillary passages and to provide such body with a coating of graphite. The graphite coating may be produced by painting or rubbing it on the body.

The desired eect may also be obtained by carburetion in a similar manner as known from carbureted cathodes.

The invention will be described with reference to the accompanying diagrammatic drawings, in which Fig. 1 indicates a tubular cathode;

Fig. 2 shows a dislike ilat cathode; and

Figs. 3, 4 and 5 are diagrammatic partial sectional views of cathode walls made in accordance with the invention.

The cathode Shown in Fig. 1 comprises a tubular emitatent f Patented Oct'. 1, 19574 ter body 1 of cylindrical or oval cross-section forming the tine passages previously referred to. The body 1 is joined with a suitable receptacle containing the emission substance 2 which migrates in operation through the tine passages of the emitter body 1 to the emission surface formed thereby. Numeral 3 indicates the heating lilament.

The cathode diagrammatically shown in Fig. 2 comprises a liat disklike emitter body 4 carrying a layer 5 of a carbonaceous material. The emitter body 4 may be a porous sintered tungsten body. The carbonaceous layer or coating 5 may be formed by a graphite layer. This layer, or any similar layer shown in other embodiments, may be applied in any desired manner, for example, by painting it on the sintered tungsten body 4. The emission material 6 is disposed within a receptacle suitably joined with the body 4. The heating filament 8 may be covered by an insulating material 7.

Fig. 3 shows a sectional view of part of the wall of an emitter body. This wall is made entirely of carbon or carbonaceous material.

Fig. 4 indicates a similar fractional sec-tional View of Y the wall of an emitter body. The wall 9 of the emitter body may be a porous tungsten body carrying a carbon or carbonaceous layer 10. The wall portion 9 contains admixtures 11. These admixtures may be any one of the metals silicon, titanium aluminum, iron, magnesium or calcium, or combinations of some or all of these metals.

Fig. 5 is a fractional sectional view through an emitter body having a composite wall. There is first the support 12 which may be made of porous tungsten. Upon this support is a carbon layer 13 carrying in turn la layer or coating 14. The latter layer may consist of one or more of the previously mentioned metals.

Either of the structures shown in Figs. 3, 4 and 5 may of course be used in cathodes of different configuration including tubular cathodes and disklike cathodes.

Changes may be made within the scope and spirit of the appended claims.

I claim:

1. In a dispenser type cathode for use in an electrical discharge tube having a porous metallic body forming an emitting surface and having means forming on the side of said body which faces away from said emitting surface a receptacle containing a supply of emissive material and having a heater for heating said material to cause migration thereof through said body to said emitting surface formed thereby; the improvement which consists in the provision on said emitting surface of a thin coating of a mixture comprising at least two elements of the group of elements consisting of carbon, silicon, titaninum, aluminum, iron, magnesium and calcium, said coating being eiective to increase the emission of said emissive material upon said emitting surface of said porous metallic `body beyond the normal emission thereof.

2. A cathode according to claim l, wherein said coating is disposed on top of said porous metallic body over a defined restricted surface portion thereof.

3. A cathode according to claim 2, wherein said coating comprises carbonaceous material.

4. A cathode according to claim 2, wherein said coating comprises graphite.

5. A cathode according to claim 3, wherein said porous metallic body is a tungsten body containing in admixture therewith at least two elements of the group of elements consisting of silicon, titanium, aluminum, iron, magnesium and calcium.

6. A cathode according to claim 1, comprising a layer of carbonaceous material disposed directly upon said emitting surface, said coating being dispsed on top of said layer.

References Cited in the file of this patent UNITED STATES PATENTS 4 Espe June 21, 1938 Williams -2.. Mar. 30, 1948 Williams Feb. 14, 1950 Lemmens et a1 Feb. 27, 1951 Coppola et al. Nov. 1, 1955 Katz June 12, 1956 

